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Metal-resin composite molding and method for manufacturing the same

Metal-resin composite molding and method for manufacturing the same description/claims

The present invention relates to a metal-resin composite molding composed of a metal portion formed from a metal bonded to a resin portion formed from a synthetic resin, and a method for manufacturing the metal-resin composite molding.

In recent years, various novel composite materials have been developed, the composite materials being made by bonding various materials together. An example is a composite molding (metal-resin composite molding) composed of a metal portion formed from a metal such as aluminum or copper bonded to a resin portion formed from a synthetic resin such as an engineering plastic. When a metal-resin composite molding is made, for example, a metal portion and a resin portion are bonded together using an adhesive by a method as disclosed in Japanese Laid-Open Patent Publication No. 2002-327070. According to the method, the surface of the metal portion is subjected to pretreatment in order to make the surface of the metal portion suitable for adhesion. As a result of this, adhesion inhibitors are removed from the surface of the metal portion. Subsequently, an adhesive such as an epoxy resin-based or acrylic resin-based type is applied to the pretreated surface of the metal portion. After the adhesive is dried, the metal portion is arranged as an insert in a mold for resin molding. Subsequently, a molding material composed of a synthetic resin is molten in the mold. Then, the molding material molten in the mold is cured thereby forming the resin portion into a predetermined shape. In this way, a metal-resin composite molding, in which a metal portion and a resin portion have been bonded together with an adhesive, is obtained.

However, the technique for manufacturing a metal-resin composite molding using an adhesive requires application and drying of the adhesive on the surface of the metal portion, in addition to the molding of the resin portion. These additional treatments increase the number of working processes.

An objective of the invention is to provide a metal-resin composite molding and a method for manufacturing the same, wherein a metal portion and a resin portion are bonded together without using an adhesive.

To achieve the foregoing objective and in accordance with one aspect of the present invention, a metal-resin composite molding composed of a metal portion formed from a metal bonded to a resin portion formed from a synthetic resin is provided. The surface of the metal portion has silanol groups. The synthetic resin contains an adhesive modifier having adhesive functional groups interacting with the silanol groups. The metal portion and the resin portion are bonded together by the interaction between the silanol groups and the adhesive functional groups.

In accordance with another aspect of the present invention, a method for manufacturing a composite molding composed of a metal portion formed from a metal bonded to a resin portion formed from a synthetic resin is provided. The method includes: applying silanol groups to the surface of the metal portion; adding an adhesive modifier having adhesive functional groups interacting with the silanol groups to the synthetic resin thereby producing a molding material; and arranging the metal portion as an insert in a mold for resin molding, melting and forming the molding material in the mold into the resin portion, and at the same time bonding the resin portion to the metal portion through the interaction between the silanol groups and the adhesive functional groups.

The present invention will be described below in more detail. The metal-resin composite molding of the present invention is a composite molding obtained by bonding a metal portion formed from a metal to a resin portion formed from a synthetic resin without using an adhesive. The following section describes the metal portion and resin portion composing the metal-resin composite molding, and the adhesion between the components.

The major part of the metal portion excluding the surface is formed into a predetermined shape by machining a metal material. The type of the metal is not particularly limited, and examples thereof include copper, nickel, tin, gold, aluminum, iron, magnesium, stainless steel, chromium, tungsten, zinc, lead, and alloys thereof.

The surface of the metal portion is subjected to ITRO treatment (silicification flame treatment) as described in Japanese Patent No. 3557194. The treatment applies silanol (SiOH) groups to the surface of the metal portion. The silanol groups activate the surface of the metal portion. The details about the ITRO treatment will be described below.

The resin portion is made by forming a molten molding material into a predetermined shape. The molding material is composed of a synthetic resin as a base material, and an adhesive modifier. The resin portion preferably contains 5 to 40% by weight of the adhesive modifier. If the content of the adhesive modifier is less than 5% by weight, adhesiveness deteriorates. On the other hand, if the content of the adhesive modifier is more than 40% by weight, releasability from the mold during molding deteriorates. The content of the adhesive modifier in the resin portion is more preferably from 10 to 30% by weight.

The synthetic resin is not particularly limited, and examples thereof include engineering plastics such as polyphenylene sulfide (PPS), polyamide (PA), and polybutylene terephthalate (PBT).

Polyphenylene sulfide is a heat-resistant crystalline polymer having a molecular structure composed of alternating phenyl groups (benzene rings) and sulfur (S) atoms. Polyphenylene sulfide features high tensile strength and bending strength. Polyphenylene sulfide is classified into two types: crosslinked type and linear type.

The crosslinked type is a polymer produced through heat treatment in the presence of oxygen during manufacturing of the polymer. The heat treatment increases the molecular weight of the polymer to the intended level. In the crosslinked type, polymer molecules are partially linked together via oxygen to form a two-dimensional or three-dimensional crosslinked structure. Therefore, the crosslinked type has higher stiffness than the linear type at high temperatures. Accordingly, the crosslinked type undergoes less creep deformation and stress relaxation. On the other hand, the linear type is a polymer subjected to no heat treatment during manufacturing of the polymer. Therefore, the polymer molecule of linear type includes no crosslinked structure. The polymer molecule of linear type is in a one-dimensional linear form. In general, the linear type has lower stiffness and slightly higher toughness and elongation than the crosslinked type.

Polyamide is a linear polymer containing a main chain composed of repeating amide bonds (—CONH—). Polyamide features, for example, excellent impact resistance and chemical resistance, and a relatively high deflection temperature under load. Examples of polyamide (PA) include polyamide 6 (PA 6), polyamide 66 (PA 66), polyamide 11 (PA 11), polyamide 12 (PA 12), and aromatic polyamide (aramid resin).

Polybutylene terephthalate is a thermoplastic and crystalline polyester-based resin. Polybutylene terephthalate is excellent in, for example, heat resistance, chemical resistance, electrical properties, dimensional stability, and moldability. In order to improve the physical properties of the base material, such as mechanical strength, heat resistance, electrical conductivity, and electrical insulation properties, the molding material may contain, for example, glass fibers or an inorganic filler.

The adhesive modifier has adhesive functional groups which interact with the silanol groups on the surface of the metal portion. Examples of the adhesive functional groups include unsaturated organic acid groups in maleic anhydride, phthalic anhydride, acrylic acid, maleic acid, and itaconic acid, and epoxy groups and glycidyl groups.

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